Periodontitis is the second stage of periodontal disease. Periodontitis is inflammation of the gum tissue that extends into the bone and erodes the bone structure by infection. The bone deterioration often causes deep pockets under the gum tissue. Deep pockets, in the range of 5 millimeters (1/5 of an inch), become filled with bacteria that are difficult or impossible to remove during routine brushing and flossing. Deep pockets need to be corrected to prevent further deterioration of the bone supporting the teeth.

Reduction of the pockets helps eliminate the bacterial accumulation by cleaning out the infection in the bone and tightening the gums around the teeth. This procedure is called osseous surgery. Osseous surgery is often augmented with bone grafting. The purpose of this procedure is to reduce the pocket depths enabling the patient to better maintain a healthy periodontal condition.